Whisk 1 1/4 cups sugar, egg yolks, lemon juice, lemon peel, and salt in large metal bowl to blend. Set bowl over large saucepan of simmering water and whisk constantly until yolk mixture is thick and fluffy and instant-read thermometer inserted into mixture registers 170°F, about 4 minutes. Remove bowl from over simmering water. Using electric mixer, beat mixture until cool, thick, and doubled in volume, about 6 minutes. Fold in chilled whipped cream. Transfer mixture to prepared loaf pan and smooth top. Tap loaf pan lightly on work surface to remove air pockets. Fold plastic wrap overhang over top to cover. Freeze semifreddo until firm, at least 8 hours or overnight. DO AHEAD Semifreddo can be made 3 days ahead. Keep frozen.

Gently mix all berries and remaining 2 tablespoons sugar in large bowl. DO AHEAD Can be made 3 hours ahead. Cover and refrigerate.